In a process of manufacturing the semiconductor device such as IC and LSI, there is performed the fact that a thin film is formed on a substrate by a reduced pressure CVD method (Chemical Vapor Deposition method). As one of such film forming methods, there is implemented the fact that a silicon film having been doped with boron is formed by the reduced pressure CVD method. Hitherto, in order to dope the boron to the silicon film, there has been used diborane. In this case, by introducing a gas from a furnace body lower part under a state that, in a reaction furnace, plural wafers have been stack-supported vertically in a boat to thereby cause the gas to vertically ascend, if there is used a reduced pressure CVD apparatus which forms the thin film on the wafer by a heat CVD method while using that gas, in-face homogeneities of a film thickness and a resistivity have been as bad as 10-20% in whole regions from a bottom region (lower part region) to a top region (upper part region) in the CVD apparatus.
There is known the fact that the above film thickness in-face homogeneity is greatly improved by using boron trichloride instead of the diborane and there is obtained such a boron-doped polycrystalline silicon film that its film thickness in-face homogeneity is 1% or less in the whole regions (refer to Patent Document 1).
Patent Document 1: JP-A-2003-178992